Because of their strength, heat resistance, and chemical resistance, polyester containers, films, and fibers are an integral component in numerous consumer products manufactured worldwide. In this regard, most commercial polyester used for polyester containers, films, and fibers is polyethylene terephthalate polyester.
Polyester resins, especially polyethylene terephthalate and its copolyesters, are also widely used to produce rigid packaging, such as two-liter soft drink containers. Polyester packages produced by stretch-blow molding possess outstanding strength, clarity, and shatter resistance, and have excellent gas barrier and organoleptic properties as well. Consequently, such lightweight plastics have virtually replaced glass in packaging numerous consumer products (e.g., carbonated soft drinks, fruit juices, and peanut butter).
Despite these recognized advantages, conventional polyethylene terephthalate resins are often unsuitable for applications requiring thermal stability, such as for automobile interiors or for outdoor applications requiring exposure to summer temperatures. Moreover, conventional polyethylene terephthalate resins do not hold up well during high temperature washings (i.e., near 100° C.).
In this regard, polycarbonate is a preferred polymeric material for it possesses not only an elevated glass transition temperature (TG) of about 150° C., but also exceptional impact strength. Accordingly, polycarbonate is frequently employed in higher temperature applications. Polycarbonate is also used as an unbreakable glass substitute in windows and eyewear lenses. Thermoplastic polycarbonate is available, for example, under the trade name LEXAN® (GE Plastics).
Similarly, polymethyl methacrylate (PMMA), an acrylic, possesses a glass transition temperature (TG) of about 105° C., which imparts respectable heat bearing capability. PMMA also has excellent clarity. Although PMMA possesses lesser impact resistance as compared with polycarbonate, it is less costly and is often used as a glass substitute, such as in windows and signs. PMMA is available, for example, under the trade names PLEXIGLAS® (Elf Atochem) and LUCITE® (Ineos Acrylics).
Polyester having satisfactory properties could provide a cost-effective alternative to polycarbonate and PMMA in many applications. In this regard, there is a need for polyethylene terephthalate resin that retains—and perhaps even improves upon—the strength and durability of conventional polyesters, yet provides improved thermal stability.